Particle pump methods and devices.

ABSTRACT

Methods and devices are provided for transfer of particulate material, such as biomass feedstocks, into and out of pressurized reactors. Improved sluice devices have an L-shaped sluice chamber having an upper, vertical component in communication with a horizontal loading chamber and a lower component in communication with a vertical reactor inlet or outlet. Piston valves seal the sluice inlet and outlet by axial displacement across the vertical component of the sluice chamber and across the vertical reactor inlet or outlet. Relative to other methods for reactor unloading, these devices consume less steam and significantly reduce furfural content of unloaded, pretreated biomass. An optional hybrid plug/sluice method of biomass feeding using the devices permits biomass loading at sluice pressures intermediate between atmospheric and reactor pressure, thereby reducing “pump cycle” time and increasing biomass throughput capacity.

This application is a divisional of co-pending application U.S. Ser. No.13/062522 which is a national stage entry of PCT/IB2010/53864,international filing date Aug. 27, 2010, which claims priority to U.S.Ser. No. 61/237301, filed Aug. 27, 2009, and to U.S. Ser. No. 61/318431,filed 29 Mar. 2010.

FIELD OF THE INVENTION

The invention relates in general to devices and methods for transfer ofparticulate material into and out of pressurized reactors and inparticular to devices and methods for feeding biomass feedstocks intoand out of pressurized hydrothermal reactors.

BACKGROUND

Commercial production of bioethanol and other useful products fromlignocellulosic biomass requires high levels of feedstock throughput, onthe order of 10 to 50 metric tons dry matter per hour. In biomassconversion systems that rely upon hydrothermal pretreatment offeedstocks prior to enzymatic hydrolysis, the scale of processing can belimited by the rate at which particulate material can be fed intopressurized pretreatment reactors.

Systems for “feeding” biomass into pressurized reactors generally fallinto one of two predominant categories—plug feeders and sluice feeders.Plug feeders are well known in the pulp and paper industry. These useloading devices such as screws, pistons, and combination piston-screwsto compact particulate material to a sufficient effective density so asto form a gas impenetrable pressure seal or “plug.” This plug is thencontinuously formed and loaded into a reactor against high pressures.Plug feeders have been reported to efficiently load against pressuresfrom 4 to 10 bar. A variety of different plug feeder schemes have beenreported. Some screw-plug feeders rely on a very long feeding screw,which permits loading at somewhat lower effective biomass plug density.Systems relying on higher effective density often utilize adisintegrator device on the pressurized reactor side to break apart thehigh density plug. See for example U.S. Pat. No. 3,841,465; U.S. Pat.No. 4,186,658; U.S. Pat. No. 4,274,786; U.S. Pat. No. 5,996,770;WO2003/050450; WO2004/105927; WO2009/005441.

Sluice feeders rely on a system of pressure locks, at least one of whichis kept closed at all times. Particulate material is loaded into asluice chamber through an open inlet valve. The inlet valve is thenclosed and the material unloaded into a high pressure reactor through anopen outlet valve. A variety of sluice feeder systems have also beenreported. See for example U.S. Pat. No. 5,095,825; SE 456,645; SE500,516; WO1993/010893; WO1993/000282; WO2003/013714.

Individual sluice feeders generally have a lower capacity but provide ahigher level of operational safety relative to plug feeders. Biomass isinvariably heterogeneous material. Thus, even a highly compressed plugcan contain channels through which potentially explosive release ofpressurized steam may occur. In providing a mechanical valve sealagainst reactor pressure at all times, sluice feeders greatly reduce therisk of explosive release.

High density plug feeders have generally been considered advantageousover sluice feeders in that they can be readily scaled to very largecapacity. However, plug feeders also have several notable disadvantages.Plug feeders have not been shown to operate effectively at pressures>10bar. They are typically operated at very high levels of feedstockcompression, in part to minimize occupational hazards. Biomass istypically pressurized to levels much higher than nominally required toseal against reactor pressure. As a consequence, plug feeders generatetremendous frictional forces between the plug and the feeding apparatus.This reduces energy efficiency and also introduces high levels ofmechanical wear-and-tear, particularly with feedstocks having high sandor silica content such as wheat straw, rice straw and corn stover.Refurbishing of the “plug screw” or other loading device in plug feedersis routine maintenance which may be required on intervals as brief as1-3 months. This introduces production inefficiencies as well as highmaintenance costs. Plug feeders also typically require that feedstocksbe subject to particle size reduction and extensive washing, whichintroduces additional process steps as well as increased energyrequirements and running costs.

These disadvantages of plug feeders have been successfully avoided on apilot production scale of 1 metric ton dry matter per hour using thesingle sluice chamber feeder system described in WO2003/013714, which ishereby incorporated by reference in entirety. Using this system, biomasscan be efficiently loaded against pressures>15 bar. Feedstocks areprocessed without extensive particle size reduction or washing, firstportioned into pre-determined portions, then force-loaded into ahorizontal sluice chamber by means of a piston screw or similar device,the axis of which is practically in line with the axis of the sluicechamber.

We have discovered a variety of means whereby this sluice system can bescaled to larger capacity with increased operational safety andefficiency.

Further, we have discovered that sluice systems provide improved meansfor removing pretreated biomass from pressurized reactors. Plug feedersdo not, themselves, provide means for removing pretreated biomass.Previously, pretreated biomass has typically been removed using “steamexplosion” systems or “hydrocyclone” systems such as those described inWO 2009/147512, which is hereby incorporated by reference in entirety.Hydrocyclone systems were previously viewed as advantageous due torelatively conservative steam losses associated with removal ofpretreated biomass. By using particle pump outlets to remove pretreatedbiomass, significant improvements over the performance of steamexplosion and hydrocyclone systems can be obtained. In particular,relative to hydrocyclone systems, concentrations of the fermentationinhibitor furfural in the pretreated biomass released from the reactorcan be reduced by more than 50%. Relative to steam explosion systems,both furfural content in released pretreated biomass and also steamlosses associated with removal of pretreated biomass can be reduced.

These and other improvements are described in detail herein.

SUMMARY

Methods and devices are provided for transfer of particulate material,such as biomass feedstocks, into and out of pressurized reactors.Improved sluice devices have an L-shaped sluice chamber having an upper,vertical component in communication with a horizontal loading chamberand a lower component in communication with a vertical reactor inlet oroutlet. Piston valves seal the sluice inlet and outlet by axialdisplacement across the vertical component of the sluice chamber andacross the vertical reactor inlet or outlet. Relative to other methodsfor reactor unloading, these devices consume less steam andsignificantly reduce furfural content of unloaded, pretreated biomass.An optional hybrid plug/sluice method of biomass feeding using thedevices permits biomass loading at sluice pressures intermediate betweenatmospheric and reactor pressure, thereby reducing “pump cycle” time andincreasing biomass throughput capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic illustration of a preferred embodiment.

FIG. 2 shows a side-angle view of a preferred embodiment actuated byhydraulic cylinders.

FIG. 3 shows a section-view of the preferred embodiment shown in FIG. 2.

FIG. 4 shows a side-angle view of a preferred embodiment actuated byelectrical drives.

FIG. 5 shows a section-view of the embodiment shown in FIG. 4.

FIG. 6 shows adaptation of a preferred embodiment for removal ofpretreated biomass from a pressurized reactor.

FIGS. 7A, 7B, and 7C show a schematic illustration of a hybridplug/sluice mode of operation of the embodiment shown in FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The single sluice chamber feeder system of WO2003/013714 provides ahorizontal sluice chamber in which the piston screw unloading device ispractically in-line with the axis of the sluice chamber. Using thissystem, guillotine-type valves are generally preferred as pressure locksfor the sluice inlet and outlet.

We have discovered that piston valves can be used at the sluice inlet byaligning the axis of the loading device at an angle to the axis of thesluice chamber, preferably perpendicular. Piston valves are advantageousin that these are less prone to clogging and mechanical wear and aremore readily scalable to large sizes than guillotine-type valves.

The axis of the loading device can be aligned at an angle to the axis ofthe sluice chamber by use of a vertical sluice chamber through whichbiomass falls by force of gravity. The risk of “bridging” is increasedwithin a vertical sluice chamber, particularly using non-flowing orcomparatively high dry matter feedstocks which have not been subject toextensive particle size reduction. Accordingly, vertical sluice chamberswere previously considered undesirable for sluice feeding biomassfeedstocks. We have discovered that “bridging” can be effectivelyavoided through use of an L-shaped sluice chamber. This has both anupper, vertical component and, also, a lower unloading segment throughwhich an unloading device adapted for force-unloading is axiallydisplaceable. By aligning the axis of the unloading device at an angleto the axis of the reactor inlet, preferably perpendicular, it is alsopossible to use piston valves as pressure locks for the sluice outlet.

The introduction of a sluice chamber having a horizontal unloadingsegment fitted with an additional device for force-unloading providessurprising resistance to sudden pressure change. This increasesoperational safety and ensures that a safety chimney, which dissipatessudden pressure release from the sluice chamber, need only beconstructed to tolerate minor pressure changes.

The use of both loading and unloading devices aligned at an angle,preferably perpendicular, with the sluice chamber and reactor inletrespectively permits a hybrid plug/sluice method of biomass feeding. Insome embodiments, compression of biomass by the loading device withinthe loading chamber and compression of biomass by the unloading devicewithin the unloading segment of the sluice chamber creates comparativelylow-density plugs. These plugs can effectively seal against pressuresintermediate between atmospheric and reactor pressure. Plug partialsealing permits a hybrid plug/sluice mode of operation in which biomassmay be loaded without fully equilibrating pressure within the sluicechamber to atmospheric pressure and in which biomass may be unloadedwithout fully equilibrating pressure within the sluice chamber toreactor pressure. This hybrid operation mode reduces “pump cycle” timeof the sluice device and accordingly increases its throughput capacity.Cycle time can be further decreased by introducing cool water mist intothe sluice chamber during depressurization.

Surprisingly, significant operational advantages can also be obtainedusing a sluice chamber feeding device, or “particle pump,” to not feedbut remove pretreated biomass from pressurized hydrothermal reactors.Most notably, concentrations of the fermentation inhibitor furfural,produced as a byproduct of hydrothermal pretreatment, that remain inpretreated biomass after unloading are significantly reduced. Whereequivalent biomass is pretreated under equivalent conditions but removedusing a sluice system compared with a hydrocyclone system, furfurallevels obtained in the insoluble fiber fraction are typically reduced byat least 50%. As is well known in the art, concentrations of furfuralproduced as a byproduct of hydrothermal pretreatment raises asignificant obstacle to effective second generation fermentationprocesses such that detoxification process steps are typically required.

Without wishing to be bound by theory, it is believed that thissurprising advantage of a particle pump outlet is due to subtleties ofthe furfural/water phase equilibrium within a pressurized hydrothermalreactor. At the relatively dilute concentrations of furfural typicallyachieved in hydrothermal pretreatment, mol %<0.5 at 35% dry matter, andin the high temperature and pressure regime of a hydrothermalpretreatment reactor, typically between about 160 to 230° C. and betweenabout 10 to 20 bar pressure, furfural is expected to exist primarily inthe vapour phase, relative to liquid phase, by a factor of at leastabout 4:1. (See e.g. R. Curtis and H. Hatt, “Equilibria infurfural-water systems under increased pressure and the influence ofadded salts upon the mutual solubilities of furfural and water,”Australian Journal of Scientific Research Series A: Physical Sciences(1948) 1:213.) During the removal cycle, using a particle pump outlet,equilibration of the outlet sluice chamber to low pressure is associatedwith venting of vapour phase from the pretreated biomass undercontrolled conditions, prior to removal, effectively stripping the greatbulk of furfural content.

Two experimental pretreatment reactors in our laboratories in Skærbæk,Denmark, having respective throughput capacities of 100 and 1000 kg/hourbiomass, were alternatively fitted with hydrocyclone biomass outlets(1000 kg/hr), as described in WO 2009/147512, or with a simplesingle-chamber horizontal sluice chamber outlet (100 kg/hr), similar tothe single-chamber sluice feeder system described in WO2003/013714. Bothsystems were used to pretreat wheat straw under equivalent conditions,to severity about 3.88, at 14 bar pressure, 190° C. Pretreated wheatstraw unloaded using both systems was pressed into a fiber and liquidfraction. The pressed fiber fractions were subsequently washed using thesame belt press washing apparatus, operated in equivalent conditions.

Washed fiber fractions from pretreated wheat straw unloaded using theparticle pump outlet were sampled on 3 separate dates, after thepretreatment system was operating at steady-state. Washed fiberfractions from pretreated wheat straw unloaded using the hydrocyloneoutlet were sampled on 6 separate dates after the pretreatment systemwas operating at steady-state. The particle-pump unloaded biomass hadsignificantly lower furfural levels, 0.79+/−0.04 g/kg, compared withhydrocyclone unloaded biomass, 1.65+/−0.24 g/kg, t,p<0.005. While directmeasurements of furfural content in the initial pressed fiber fractionfrom the hydrocyclone unloaded biomass were not made, these values canbe readily extrapolated from the direct washed fiber values by applyingan averaged pressed/washed furfural ratio obtained using this system.Furfural content in pressed fiber fractions obtained using the particlepump outlet was significantly lower than furfural content of thecalculated pressed fiber fraction obtained using the hydrocycloneoutlet, 1.59+/−0.14 g/kg compared with 4.61+/−0.58 g/kg, t, p<0.003.

The particle pump outlet provides significant reduction in furfuralcontent of the insoluble fiber fraction obtained from pretreatedbiomass, at least 50%, apparently as a simple effect of controlled steamventing during the unloading (depressurization) cycle. It will bereadily understood by those skilled in the art that particle pumpoutlets may be optimized to achieve even greater reductions of furfuralcontent. The simple single-chamber, horizontal sluice chamber systemused in the experiments reported here could achieve at least 50%reductions in furfural content, where depressurization from 14 bar to 2bar was conducted in a cycle of about 1 minute, and where temperaturewas reduced from 190° C. to about 100° C. Biomass was ejected at about 2bar, at about 100° C. Much deeper reductions in furfural content couldbe achieved by simply ejecting the biomass at 2 bar into an outletchamber, in which pressure was further reduced to sub-atmosphericlevels, preferably between 50 and 200 torr, and preferably attemperatures above 140° C. as described in U.S. Pat. No. 4,912,237,which is hereby incorporated by reference in entirety. Through routineexperimentation, one skilled in the art can readily optimize biomassejection using a particle pump outlet to conditions that achieve optimalfurfural reduction.

Particle pump methods of removing pretreated biomass are, in any case,advantageous relative to steam explosion methods in that steamconsumption is reduced. “Cooking steam” consumption with ourhydrothermal reactor fitted with a particle pump outlet averagedapproximately 160 kg/steam per 1000 kg biomass feedstock pretreated. Incontrast, similar reactors operated at similar pretreatment severitiesbut fitted with steam explosion outlets typically report higher “cookingsteam” consumption, on the order of 250-350 kg/steam per 1000 kg biomassfeedstock pretreated.

Particle pump outlets are also advantageous relative to steam explosionin terms of reduction of furfural content in pretreated biomass removedfrom the reactor. Again without wishing to be bound by theory, it isbelieved that pretreated biomass removed from the reactor throughparticle pump outlets have lowered furfural content relative to materialremoved through steam explosion outlets also due to subtleties of thefurfural/water phase equilibrium. In steam explosion, pretreated biomassis suddenly released from high pressure reactor conditions, which favourliquid phase of water and which favour vapour phase of furfural at thelow concentrations of furfural typically experienced. At atmosphericpressure, vapour phase of water in the hot biomass is favoured,resulting in an explosive vaporization of water within the hot biomassthat disrupts cellulose chains, contributing to a beneficial overallpretreatment effect. However, as the steam-exploded biomass cools totemperatures below 100° C., or at least below 97.9° C., furfural isexpected to condense into the biomass. See e.g. G. H. Mains, Chem. Met.Eng. (1922) 26:779. Accordingly, much higher furfural levels arereported in steam-exploded biomass treated at similar severities andunloaded at similar pressures than the furfural levels reported here inpretreated biomass unloaded through a particle pump outlet. See e.g. L.Hongquiang and C. Hongzhang, “Detoxification of steam-exploded cornstraw produced by an industrial-scale reactor,” Process Biochemistry(2008) 43:1447.

In some embodiments, the invention provides an apparatus for transfer ofparticulate matter into or out of a pressurized reactor comprising:

-   (a). A loading chamber,-   (b). A loading device situated within the loading chamber,-   (c). An L-shaped sluice chamber having an upper vertical component    in communication with the loading chamber and having a lower    component in communication with a vertical reactor inlet or outlet,-   (d). A sluice inlet piston valve which is axially displaceable    across the vertical component of the sluice chamber and which is    adapted to seal the opening from the loading chamber into the    vertical component of the sluice chamber,-   (e). An unloading device which is axially displaceable within the    lower component of the sluice chamber, and-   (f). A sluice outlet piston valve which is axially displaceable    across the vertical reactor inlet or outlet and which is adapted to    seal the opening from the lower component of the sluice chamber into    the reactor inlet or outlet.

The loading chamber has at least one opening through which biomassfeedstocks may be introduced and is aligned in communication with (i.e.,having an opening to) the vertical component of an L-shaped sluicechamber. In some embodiments, the loading chamber provides a containmentin which biomass feedstock can be compressed, portioned or otherwiseconditioned prior to force-loading into the sluice chamber. In preferredembodiments, the loading chamber is approximately horizontal andcommunication with the vertical component of the sluice chamber isapproximately perpendicular. In other embodiments, the loading chambermay be upwardly or downwardly sloping, aligning with the verticalcomponent of the sluice chamber at an angle between about 70-120degrees. In some embodiments, the loading chamber is equipped with anaxially displaceable loading device that compresses biomass feedstockwhile the sluice inlet valve is closed and that force-loads compressedbiomass into the sluice chamber. In other embodiments, the loadingchamber may simply be a container within which a loading device operatesto force-load biomass into the sluice chamber.

A suitable loading device may comprise a screw conveyor, a piston-screw,or a piston. In some embodiments, it is advantageous to compress biomassfeedstocks during loading. Thus in some embodiments the loading deviceis able to provide compression of biomass feedstocks to within the rangeof about 200-400 kg/m³. In preferred embodiments, the loading device isa piston screw. Also in preferred embodiments, the device is rotable ineither clockwise or counter-clockwise orientations. Mechanicalresistance to the motor which rotates the piston screw can readily becalibrated to provide an accurate measurement of biomass compaction. Insome embodiments, biomass loading of the loading chamber is typicallyconducted by first compressing biomass against a closed sluice inletvalve, then loading the compressed biomass into the sluice chamber byaxial displacement of the loading device. In other embodiments, wherecompression of biomass during loading is not desired, the loading deviceforce-loads biomass directly into the sluice chamber through an opensluice inlet valve, achieving little compression of the biomass. In someembodiments, especially where compression of biomass is desired, theloading device is axially displaceable within the loading chamber. Inother embodiments, especially where compression of biomass is notdesired, the loading device may be fixed within a relatively smallloading chamber that effectively provides little more than a containerwithin which biomass is collected and force-loaded by the loadingdevice.

The sluice chamber is L-shaped. As used herein, the term “L-shaped”refers to a device having both an upper, vertical component and a lowercomponent. The term “vertical” as used herein means aligned with thedirection of the force of gravity, +/−10%. In preferred embodiments, thelower component is approximately horizontal and communication betweenthe upper and lower components is approximately perpendicular. In otherembodiments, the lower component may be upwardly or downwardly sloping,aligning with the vertical component of the sluice chamber at an anglebetween about 70-120 degrees. In preferred embodiments, the verticalcomponent of the sluice chamber has an internal diameter larger than theinternal diameter of the loading chamber, so as to further reduce therisk of biomass bridging. Although the term “L-shaped” is used, oneskilled in the art will readily understand that either the vertical orthe lower component may be longer than the other, or both may be ofequivalent length.

In some embodiments, the sluice chamber can be equipped with means forinjecting cool water mist. In general, pressurization to reactorpressure is comparatively faster than de-pressurization to loadingpressure. It is thus advantageous to enhance the rate of sluice chamberdepressurization, since this in turn reduces cycle time of sluicechamber loading, pressurization, unloading, and depressurization. Coolwater mist is believed to enhance the rate of depressurization byfacilitating condensation of pressurized steam.

The lower component of the sluice chamber, or unloading segment, isaligned in communication with a vertical reactor inlet or outlet. Inpreferred embodiments, the unloading segment is approximately horizontaland communication with the vertical reactor inlet or outlet isapproximately perpendicular. The unloading segment is equipped with anaxially displaceable unloading device that, optionally, compressesbiomass feedstock while the sluice outlet valve is closed and thatforce-unloads biomass into the vertical reactor inlet or out of thereactor outlet. Alternatively, the unloading device may force-unloadbiomass directly through an open sluice outlet valve, without achievingcompression of biomass during unloading.

Similar to the loading device, a suitable unloading device may comprisea screw conveyor, a piston-screw, or a piston and, in preferredembodiments, is rotable in either clockwise or counter-clockwiseorientations.

The angular connections between the loading chamber and the upper,vertical component of the sluice chamber and between the lower componentof the sluice chamber and the vertical reactor inlet or outlet permituse of piston valves as pressure locks. Piston valves are comparativelyless prone to clogging and mechanical wear and are more readily scalableto large sizes than other valve systems such as guillotine type valves,which are preferred, where the axis of the loading device is in-linewith the axis of the sluice chamber. The piston valves are axiallydisplaceable across the vertical component of the sluice chamber andacross the vertical reactor inlet or outlet and are adapted to seal thesluice inlet and outlet.

In preferred embodiments, both the sluice inlet and the sluice outletpiston valves comprise a rotating disc. Rotation of the disc-shapedvalve during closure clears the sluice inlet and outlet valve seat ofbiomass, which can otherwise accumulate.

In preferred embodiments, the sluice inlet and outlet piston valvesdisplace substantially in line with the displacement of the loading andunloading devices respectively. In some embodiments, the sluice inletand/or sluice outlet valve may be fitted with blades or other means fordisintegrating compressed biomass. Disintegration means helps avoidentry into the reactor of compressed biomass “clumps,” which caninterfere with even heating of biomass and result in suboptimalpretreatment.

In some embodiments, the loading device, unloading device and pistonvalves may be actuated by hydraulic cylinders. These are reliable andreadily scalable to large sizes. However, these require approved valvesand control programs as well as regular inspection of the mechanicalcomponents. Accordingly, in some embodiments electrical driven actuatorsmay be used, which generally have improved energy efficiency as well asa simpler and more cost optimal design. The electrical-powered actuatorsare also self-locking, in that these can only actuate if the motor ispowered, resulting in improved safety relative to hydraulic cylinders.

In some embodiments, the vertical reactor inlet may comprisedisintegrator means or other means for facilitating even heating ofloaded biomass within the reactor.

FIG. 1 provides a schematic illustration of one preferred embodimentthat is able to optionally operate in hybrid plug/sluice mode of biomassfeeding. The device has a horizontal loading chamber (1) equipped with aloading device, piston screw (2), that is rotable and axiallydisplaceable within the loading chamber (1). An L-shaped sluice chamber(3) is provided that has both an upper, vertical component (3 a), inperpendicular communication with the loading chamber (1), and also alower, horizontal component or unloading segment (3 b) equipped with anunloading device, piston screw (4), that is rotable and axiallydisplaceable within the unloading segment (3 b). The loading chamber canbe opened or sealed by a sluice inlet piston valve (5 a), which isaxially displaceable across the vertical component of the sluicechamber, which is adapted to seal the opening from the loading chamberto the sluice chamber, and which opens and closes in line with thedisplacement of the loading piston screw. The unloading segment (3 b) ofthe sluice chamber is in perpendicular communication with a verticalreactor inlet (6). The unloading segment can be opened or sealed by asluice outlet piston valve (5 b), which is axially displaceable acrossthe vertical reactor inlet (6), which is adapted to seal the openingfrom the lower, horizontal component of the sluice chamber to thereactor inlet, and which opens and closes in line with the displacementof the unloading piston screw. The reactor is equipped with a feedingscrew (7) that carries loaded feedstock through the reactor to an outletfrom which pretreated material emerges. Biomass feedstock ispre-portioned into pre-defined quantities and fed to the loading chamberthrough at least one opening (8) via a chute or hopper (9). Thepreferred particle pump embodiment shown is further equipped with abiomass level sensor (10 a), that detects the level of accumulatedfeedstock material awaiting force-loading into the loading chamber (1),and a level sensor (10 b) that detects the level of accumulatedfeedstock material awaiting force-unloading through the unloadingsegment (3 b). The device is further equipped with a valve (11) which,during pressure adjustment, releases pressurized steam from the sluicechamber to process solution recycling or introduces fresh steam, andvalve (12) that introduce pressurized reactor steam into the sluicechamber during pressure adjustment. The device is further equipped witha safety chimney (13) and a cool water mist injector (14) that injectscool mist into the sluice chamber to accelerate depressurization toloading pressure.

FIG. 2 provides a side-angle view of a preferred embodiment of thedevice. In this view, the loading chamber (1), an opening to the loadingchamber through which biomass is fed (8), the loading device (2), andthe inlet piston valve (5 a) can be discerned in the upper portion ofthe device. The unloading device (4), the outlet piston valve (5 b) andthe reactor inlet (6) can be discerned in the lower portion of thedevice. The upper and lower portions of the device as shown are arrangedin an arbitrary orientation. The upper and lower portions canalternatively be arranged parallel or at any angle that suits spacelimitations or other requirements.

FIG. 3 provides a section-view of the embodiment shown in FIG. 2. Thisembodiment is adapted to sustain throughput of at least 4 metric tonsdry matter per hour into a reactor pressurized to 15 bar. The loadingchamber (1) is cylindrical, about 2 meters in length, having an internaldiameter of about 0.7 meters, and fitted with grooves that guidedisplacement of the loading piston-screw. The loading piston-screw (2)comprises a screw component about 0.7 meters in length, and is adaptedto displace axially within the loading chamber. The unloading segment (3b) of the L-shaped sluice chamber is similarly cylindrical, having aninternal diameter of about 0.7 meters. The vertical component (3 a) ofthe L-shaped sluice chamber is similarly cylindrical but has largerinternal diameter, about 1 meter. The biomass opening (8), sluice inletpiston valve (5 a), unloading piston screw (4), reactor inlet (6), andsluice outlet piston valve (5 b) are also shown.

FIG. 4 provides a side-angle view of one alternative embodiment that isgenerally not adapted for hybrid plug/sluice mode of biomass feeding. Inthis embodiment, the loading chamber (1) is essentially simply acontainer with an opening (8) to a biomass feed chute within whichcontainer the loading device (2) operates. The loading device (2),sluice inlet piston valve (5A), the unloading piston screw (4) and thesluice outlet piston valve (5B) are driven by electrical-poweredactuators.

FIG. 5 provides a section-view of the embodiment shown in FIG. 4. Thisembodiment is adapted to sustain throughput of at least 10 metric tonsdry matter per hour into a reactor pressurized to 15 bar. The loadingchamber (1) provides little more than a containment for the loadingdevice (2). The loading device (2) comprises two fixed screw conveyors,diameter about 0.45 m, that provide little compression of the biomassduring loading. The vertical component of the sluice chamber (3A) isabout 1.8 m in length, shorter than the unloading segment of the sluicechamber (3B) which is about 2.8 m in length. Both components of thesluice chamber have diameter about 1.0 m. In preferred modes ofoperation where biomass is fed into a pressurized reactor, the deviceloads biomass without appreciable compression through an open sluiceinlet valve. The sluice inlet valve is closed, and sluice chamberpressure equalized to approximately reactor pressure. The sluice outletvalve is then opened and biomass force unloaded by screw action andaxial displacement of the unloading device (2).

In some embodiments, the invention provides an apparatus for removingpretreated biomass from a pressurized hydrothermal reactor comprising

-   -   A sluice chamber loading device    -   A sluice chamber    -   A sluice chamber inlet valve adapted to seal an opening to        reactor pressure when closed    -   A sluice chamber outlet valve adapted to seal an opening to        atmospheric or outlet pressure when closed and adapted for        non-explosive release of pretreated biomass    -   A sluice chamber unloading device, and    -   A biomass outlet adapted for non-explosive release of pretreated        biomass.

A sluice chamber as used herein is a chamber which alternately can beopened to one of two pressure zones, while maintaining a pressure tightseparation from the other pressure zone. Non-explosive release refers torelease in such manner that biomass is substantially depressurizedrelative to reactor pressure before release. Atmospheric pressure asused herein includes levels up to about 0.3 bar above atmosphericpressure. Outlet pressure refers to a pressure lower than reactorpressure, but somewhat above or below atmospheric pressure at whichpretreated biomass is removed from a pressurized reactor. The sluicechamber outlet valve can be adapted for non-explosive release ofpretreated biomass by having a cross-sectional area approximately thesame or greater than the cross-sectional area of the sluice chamber.Biomass outlet refers to a channel or chamber or combination ofchannels, conveyances and chambers through which pretreated biomass isremoved from the pressurized reactor. The biomass outlet can be adaptedfor non-explosive release by having an opening to the sluice chamberoutlet valve that has an aperture of approximately the same or greatercross-sectional area as the valve itself. In some embodiments, theremoval device may be fitted with an outlet chamber that is adapted toprovide variable temperature and pressure conditions. By controllingpressure conditions in the outlet chamber, pretreated biomass removedfrom a pressurized reactor can be subject to physical chemicalmanipulations aimed at further reducing the content of fermentationinhibitors or other components in the pretreated biomass prior tofurther processing. For example, in some embodiments, the removal devicemay be fitted with an outlet chamber that provides sub-atmosphericpressures, preferably within the range of about 50 to 200 torr, at atemperature of above about 140° C. to further strip furfural frompretreated biomass prior to further processing.

In preferred embodiments, the device is adapted to vent steam duringdepressurization of the sluice chamber in such manner that pretreatedbiomass within the sluice chamber experiences an environment havingsubstantially lowered furfural content prior to removal from thereactor.

The device is preferably fitted with ventilation valves that can beregulated so as to release reactor steam and thereby depressurize thesluice chamber in a process that is comparatively gradual relative tosteam explosion. In preferred embodiments, the device can be fitted withseparate ventilation valve systems that ventilate steam from reactorpressures, typically 10-20 bar, down to intermediate levels ofpressures, for example 3 bar, and from intermediate levels of pressuredown to outlet pressures. It will be readily understood that theseparate ventilations systems may comprise two, three, four or morestages, for example, from 15 to 10 bar, from 10 to 8, from 8 to 5, from5 to 3, and from 3 to 1. Steam ventilated in each of the separatesystems can then be recycled to different production processes such asdrying systems, evaporation systems, biomass preheating and otherprocesses. In one preferred embodiment, the device has two ventilationvalve systems, one that ventilates from 15 bar to 3 bar and a secondthat ventilates from 3 bar to atmospheric.

Any of the embodiments of the transfer apparatus described here couldprovide suitable removal devices by appropriate adaptation andorientation of the sluice chamber and the sluice chamber inlet andoutlet valves and by adaptation of the reactor outlet for non-explosiverelease of pretreated biomass. Suitable loading and unloading devicesare as described previously. The sluice chamber need not be limited toL-shaped embodiments but may be arranged in any suitable configuration.The sluice chamber inlet and outlet piston valves need not be limited topiston valves but may be arranged in any suitable configuration. Any ofthe embodiments of the sluice devices described in WO 2003/013714 couldprovide suitable removal devices by appropriate adaptation andorientation of the sluice chamber and the sluice chamber inlet andoutlet valves and by introduction of a biomass outlet adapted fornon-explosive release of pretreated biomass.

FIG. 6 shows adaptation of the embodiment shown in FIG. 5 for use as aremoval device according to the invention. Shown are sluice chamberloading device (17), sluice chamber (18), sluice chamber inlet valve(19), opening to reactor pressure (20), sluice chamber outlet valve(21), opening to atmospheric or outlet pressure (22),sluice chamberunloading device (23), and biomass outlet adapted for non-explosiverelease of pretreated biomass (24).

In some embodiments, the invention provides a method for removingpretreated biomass from pressurized hydrothermal reactors, comprising

-   -   Loading pretreated biomass from a pressurized reactor into a        sluice chamber through an open inlet valve that is adapted to        seal an opening to reactor pressure when closed, while the        outlet valve that is adapted to seal an opening to atmospheric        or outlet pressure when closed is closed    -   Closing the inlet valve,    -   Depressurizing the sluice chamber from reactor pressure to        atmospheric or outlet pressure    -   Opening the outlet valve,    -   Unloading the pretreated biomass at atmospheric or outlet        pressure,    -   Closing the outlet valve, and    -   Repressurizing the sluice chamber to reactor pressure prior to        opening the inlet valve for an additional removal cycle.

Preferred embodiments are characterized by depressurization of thesluice chamber in such manner that pretreated biomass within the sluicechamber experiences an environment having substantially lowered furfuralcontent prior to removal from the reactor. In preferred embodiments,furfural content of the insoluble fiber content of unloaded biomass isless than 50% of furfural content within the reactor. In someembodiments, depressurization is accomplished by means of separateventilation valve systems that ventilate steam from reactor pressures,typically 10-20 bar, down to intermediate levels of pressures, forexample 3 bar, and from intermediate levels of pressure down to outletpressures. In one preferred embodiment, depressurization is accomplishedusing two ventilation valve systems, one that ventilates from 15 bar to3 bar and a second that ventilates from 3 bar to atmospheric. Inpreferred embodiments, steam ventilated during depressurization isrecycled to use in further production processes such as drying systems,evaporation systems, or biomass preheating. In some embodiments, theprocess is further characterized by subjecting the unloaded biomass tofurther adjustments of pressure and temperature in a biomass outletchamber. In preferred embodiments, the unloaded biomass is subject toconditions of pressure between about 50 torr and 200 torr, or betweenabout 200 torr and 700 torr, and temperatures of at least 140° C. Inpreferred embodiments, pressure within the sluice chamber isdepressurized from about 15 bar to about 0.3 bar over a period of about40 seconds.

In some embodiments, the invention provides a method for loading biomassfeedstock into a pressurized reactor comprising:

-   (a). force-loading biomass into a loading chamber that is in    communication with the upper, vertical segment of an L-shaped sluice    chamber, achieving compression of biomass while the sluice inlet    valve is closed,-   (b). adjusting sluice chamber pressure to a loading pressure that is    substantially atmospheric or intermediate between atmospheric and    reactor pressure-   (c). opening the sluice inlet valve-   (d). force-loading a quantity of biomass into the sluice chamber at    loading pressure,-   (e). closing the sluice inlet valve-   (f). adjusting sluice chamber pressure to an unloading pressure that    is substantially reactor pressure or a pressure intermediate between    atmospheric and reactor pressure-   (g). force-unloading biomass from the upper, vertical segment of the    sluice chamber into a lower segment of the sluice chamber that is in    communication with a vertical reactor inlet, optionally achieving    compression of biomass while the sluice outlet valve is closed-   (h). opening the sluice outlet valve, and-   (i). force-unloading biomass into the vertical reactor inlet while    the sluice chamber is equilibrated to unloading pressure.

In some modes of operation, some quantity of compressed biomass can beloaded into the sluice chamber with each cycle of inlet valve openingwhile some quantity remains in the loading chamber. This remainingmaterial forms a partial “plug” that, when compressed to within therange of about 200-400 kg/m³, and having a volume of at least about 0.1m³, can maintain a pressure seal for the duration of one cycle of inletvalve opening up to a difference pressure of about 3 bar.

The term “one cycle of inlet valve opening” refers to the time requiredfor inlet valve opening, force-loading of a portion of biomass into thesluice chamber, and inlet valve closing. In the embodiment shown in FIG.2, one cycle of inlet valve opening is typically between about 10 and 16seconds. The quantity of biomass that can be loaded in one cycle ofinlet valve opening is between about 75 and 150 kg dry matter. Otherembodiments can readily be conceived which can handle larger quantitiesof biomass.

In providing a partial pressure seal, the partial “plug” permits ahybrid plug/sluice mode of operation. This is advantageous because, inthis mode, the sluice chamber can be loaded at a loading pressure thatis intermediate between reactor and atmospheric pressure. This reducespump cycle time, since the sluice chamber may be loaded at a pressurethat is not fully depressurized to atmospheric pressure. In theembodiment shown in FIG. 2, operating at 15 bar reactor pressure, of thetime required to depressurize from 15 to 0.3 bar difference pressure,about 30% is typically required to depressurize from 3 to 0.3 bar. Thus,loading at 3 bar difference pressure significantly reduces cycle time.Reduced pump cycle time accordingly increases throughput capacity of thedevice.

The term “pump cycle” refers to the overall process of inlet valveopening, biomass force-loading, inlet valve closing, loading chamberre-loading, unloading segment loading, sluice pressurization tounloading pressure, outlet valve opening, biomass force-unloading,outlet valve closing, and sluice depressurization to loading pressure.Some of the functions can be arranged concurrently to optimize pumpcycle time.

In the hybrid plug/sluice mode of operation, between each cycle of inletvalve opening, fresh biomass is loaded in the loading chamber behind thepartial “plug” that is left remaining from the previous cycle.

A similar partial “plug” may be left remaining in the unloading segmentof the sluice chamber with each cycle of outlet valve opening. Thismaterial similarly forms a partial “plug” that, when compressed towithin the range of about 200-400 kg/m³, and having a volume of at leastabout 0.1 m³, can maintain a pressure seal for the duration of one cycleof outlet valve opening up to a pressure difference of about 3 barbetween reactor pressure and sluice unloading pressure. In theembodiment shown in FIG. 2, operating at 15 bar reactor pressure, of thetime required to pressurize the sluice chamber from 0.3 bar to 15 bardifference pressure, about 50% is typically required to pressurize from12 to 15 bar. Thus, unloading at 3 bar difference pressure (e.g, 12 bar)significantly reduces cycle time and increased throughput capacity ofthe device.

Devices of the invention can also be effectively and efficiently used instandard sluice modes of operation where the loading chamber andunloading segment are fully emptied on each cycle of inlet and outletvalve opening. However, in these modes, the sluice chamber is generallyadjusted to a loading pressure that is substantially atmospheric, about0.3 bar or less above atmospheric pressure, and an unloading pressurethat is substantially reactor pressure, about 0.3 bar or less differencepressure.

Devices of the invention can be used to load against reactors having anypressures, for example, from 5 to 40 bar, and higher. In hybridplug/sluice modes of operation, a suitable intermediate loading pressureis typically within the range of about 0.3 to 3 bar above atmospheric,while a suitable unloading pressure is typically within the range ofabout 3 to 0.3 bar difference pressure.

FIGS. 7A, 7B, and 7C show a schematic illustration of a hybridplug/sluice mode of operation. As shown in FIG. 7A, at the beginning ofthe pump cycle in a hybrid plug/sluice mode of operation, partial plugs(16 a,b) remain in both the loading chamber (1) and in the unloadingsegment of the sluice chamber (3B). Biomass (15) is force-loaded byscrew action of the loading device (2) into the loading chamber behindthe partial plug (16 b) while both sluice inlet valve (5A) and sluiceoutlet valve (5B) are closed.

As shown in FIG. 7B, in the loading cycle, the sluice inlet valve (5A)is open, the sluice outlet valve (5B) is closed, and pressure in thesluice chamber (3A, 3B) has been adjusted to a loading pressure of about3 bar above atmospheric. A short term seal was provided by the partialplug remaining in the loading chamber from the previous loading cycle,in combination with the loaded biomass itself. Biomass (15) isforce-loaded into the vertical component of the sluice chamber (3A) bypiston displacement of the loading device (2) and further compressed byscrew action of the unloading device (4) into the unloading segment ofthe sluice chamber (3B) behind the partial plug (16 a) remaining fromthe previous unloading cycle. A partial plug (16 b) is left remaining inthe loading chamber for the next loading cycle.

As shown in FIG. 7C, in the unloading cycle, the sluice outlet valve(5B) is open, the sluice inlet valve (5A) is closed, and pressure in thesluice chamber (3A, 3B) has been adjusted to an unloading pressure about3 bar lower than reactor pressure. A short term seal was provided by thepartial plug remaining from the previous unloading cycle, in combinationwith the unloaded biomass itself. Biomass (15) is force un-loaded intothe reactor inlet (6) by piston displacement of the unloading device(4). A partial plug (16 a) is left remaining in the unloading segment(3B) for the next unloading cycle. Concurrently, biomass (15) isforce-loaded by screw action of the loading device (2) into the loadingchamber (1) behind the partial plug (16 b) left remaining from theprevious loading cycle.

The description of preferred embodiments is representative only and notintended to limit the scope of the invention as defined by the claims.

1. An apparatus for removing pretreated biomass from a pressurizedhydrothermal reactor comprising (a). A sluice chamber loading device(b). A sluice chamber (c). A sluice chamber inlet valve adapted to sealan opening to reactor pressure when closed (d). A sluice chamber outletvalve adapted to seal an opening to atmospheric or outlet pressure whenclosed and adapted for non-explosive release of pretreated biomass (e).A sluice chamber unloading device, and (f). A biomass outlet adapted fornon-explosive release of pretreated biomass.
 2. The apparatus of claim 1further comprising separate ventilation valve systems that ventilatesteam from reactor pressures down to intermediate levels of pressuresand from intermediate levels of pressure down to outlet pressures. 3.The apparatus of claim 2 wherein the separate ventilation valve systemsventilate in two pressure stages.
 4. The apparatus of claim 3 whereinone stage ventilates from 15 bar to 3 and one stage ventilates from 3bar to atmospheric pressure.
 5. The apparatus of claim 2 wherein theseparate ventilation valve systems ventilate in three or more stages. 6.The apparatus of claim 1 further comprising an outlet chamber that isadapted to provide variable temperature and pressure conditions.
 7. Theapparatus of claim 6 wherein the outlet chamber is adapted to providetemperature of at least 140° C.
 8. The apparatus of claim 1 wherein thesluice chamber is L-shaped.
 9. The apparatus of claim 1 wherein thesluice chamber loading device comprises a screw conveyor.
 10. Theapparatus of claim 1 wherein the sluice chamber unloading devicecomprises a piston screw.
 11. A method for removing pretreated biomassfrom pressurized hydrothermal reactors comprising (a). Providing areactor unloading device comprising a sluice chamber that is fitted withventilation valves that can be regulated so as to release reactor steamand thereby depressurize said sluice chamber in a process that iscomparatively gradual relative to steam explosion and that furthercomprises a sluice chamber loading device and a sluice chamber unloadingdevice, (b). Using said reactor unloading device to load pretreatedbiomass from a pressurized reactor into the sluice chamber through anopen inlet valve that is adapted to seal an opening to reactor pressurewhen closed, while the outlet valve that is adapted to seal an openingto atmospheric or outlet pressure when closed is closed, (c). Closingthe inlet valve, (d). Depressurizing the sluice chamber to atmosphericor outlet pressure, (e). Opening the outlet valve, (f). Unloading thepretreated biomass at atmospheric or outlet pressure, (g). Closing theoutlet valve, and (h). Repressurizing the sluice chamber prior toopening the inlet valve for an additional removal cycle.
 12. The methodof claim 11 wherein furfural content of the insoluble fiber fraction ofunloaded biomass is less than about 50% of the furfural content withinthe reactor.
 13. The method of claim 11 wherein depressurization isaccomplished by means of separate ventilation valve systems thatventilate steam from reactor pressures down to intermediate levels ofpressures and from intermediate levels of pressure down to outletpressures.
 14. The method of claim 13 wherein the separate ventilationvalve systems comprise two stages.
 15. The method of claim 13 whereinthe separate ventilation valve systems comprise three or more stages.16. The method of claim 11 wherein steam ventilated duringdepressurization is recycled to use in further production processes suchas drying systems, evaporation systems, or biomass preheating.
 17. Themethod of claim 11 further comprising subjecting biomass to furtheradjustments of temperature and pressure in an outlet chamber.
 18. Themethod of claim 17 wherein the pressure in the outlet chamber isadjusted within the range 50 to 200 torr.
 19. The method of claim 17wherein the pressure in the outlet chamber is adjusted within the range200 to 700 torr.
 20. The method of claim 17 wherein the temperature inthe outlet chamber is adjusted to at least 140° C.